From: http://smt.pennnet.com/Articles/Article_Display.cfm?&Section=Articles&SubSection=Display&ARTICLE_ID=84836
Baking is a bit more complicated than many people realize. There are baking recommendations for pre- and post-dry pack based on level and package thickness. Pre-baking is used to prepare components for dry packing, while post-baking is used to recondition components after floor life expiration. Review and follow the time/temperature recommendations for baking in J-STD-033. Baking temperatures can decrease lead solderability by oxidizing the leads or causing excessive intermetallic growth. Do not store components in an oven at baking temperature. Remember, high-temperature trays can be baked at 125°C, while low-temperature trays cannot be baked at temperatures higher than 40°C. IPC post-bake recommendations after floor life has expired are: Package thickness less than or equal to 1.4 mm: For levels 2a through 5a, bake time ranges from 4 to 14 hours at 125°C, or 5 to 19 days at 40° C. Package thickness less than or equal to 2.0 mm: For levels 2a through 5a, bake time ranges from 18 to 48 hours at 125°C, or 21 to 68 days at 40°C. Package thickness less than or equal to 4.0 mm: For levels 2a through 5a, bake time is 48 hours at 125°C, or 67 or 68 days at 40°C. On Thu, 2006-06-08 at 08:58 -0400, Randall Nortman wrote: > I've got some LQFP chips that I've been storing, with the bag opened, > for a bit longer than I really should have. The indicators on the > humidity cards have started to turn pink, so I'm worried that they > will have absorbed too much humidity and if I try to reflow them now, > they'll "popcorn" (i.e., trapped moisture turns to steam and > evaporates, cracking the package and/or die). Anybody have any > suggestions on the best way to do this using common household > equipment? I guess I just stick them in an oven at lowish temperature > for a while, but what temperature and for how long? I checked the > datasheets for the chips (Atmel AT91SAM7X256 and Micrel KS8721CL) and > didn't see any useful information.
